Protective



(No Model.)

A. S. WILLIAMS. PROTECTIVE APPLIANCE FOR ELECTRICAL APPARATUS.

Patented Aug. 17,1897.

UNITED STATES PATENT OFFICE.

ARTHUR S. l/VILLIAMS, OF. NETVTON, MASSACHUSETTS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

PROTECTIVE APPLIANCE FOR ELECTRICAL APPARATUS.

SPECIFICATION forming part of Letters Patent No. 588,206, dated August 17, 1897.

Application filed May 7, 1897. Serial No. 635,542. (No model.) I

To all whom it may concern.- thereof, an insulated pin extending from the Be it known that I, ARTHUR S. lVILLIAMs, opposite end through the coil, and a tube residing at N eWton, in the county of Middleconcentric with the pin soldered to the bobseX and State of hlassachusetts, haveinvented bin of the coil. lVhen an abnormal current certain Improvements in Protective Applicontinues upon the line for a suflicientlylong ances for Electrical Apparatus, of which the time, the solder becomes melted and the confollowing is a specification. centric tube is forced away from the bobbin, In providing means for the protection of thereby opening the circuit, and the pin or a electrical apparatus from the destructive efcontact-spring impelled thereby is brought 1o fects of abnormal currents it is well under-. into contact with a ground-plate, a path to stood that separate and distinctive devices ground being thus provided for the line end must be used to guard against the different or side of the opened circuit, as will be more classes of such currents. Protective applifully described hereinafter. ances of one kind, in which an air-gap in the I prefer to describe the invention in asso- 15 grounded branch is the distinctive feature, ciation with the grounding-plate of a teleare used to guard the apparatus in the circuit phone-circuitdistributing frame, such as is 7 from high potential charges or discharges. shown in Patent No. 507,424, dated October A Ordinary fuses and tube-incloscd fuses are 24, 1892, granted to Ford and Lenfest.

employed to afford protection against cur In the accompanying drawings, Figure 1 is 20 rents of great strength or volume, while for across-section of the upright grounding-plate, protection against abnormal currents, which, upon which a plurality of protective applibeing relatively weak, are usually denomiances are located, as shown and described in nated sneak-currents, and which if they said patent. Fig. 2 represents the different persistforaconsiderable time gradually raise parts of my protective appliance separated 2 5 the temperature of the fine wires of the helito disclose their arrangement with relation ces of the instruments, it is common to emto each other. Figs. 3 and 4 are sections of ploy in the circuit some metal or alloy which the invention, illustrating its construction will melt or soften and open the circuit and and operation; and Fig. 5 is a section on line also sometimes ground it before the said heliy 1 of Fig. 3.

o ces are heated to a dangerous degree. 1 represents a vertical iron plate consti- So The present invention relates mainly to ap tuting that part of the distributing-frame to pliances which are used for the purpose of which the circuits entering a telephone cenprotection against these so-callcc sneaktral ofiiceare connected before they terminate currents, which are especially dangerous to at the switchboard. The protective appli- 3 5 switchboard-Wires and telephone apparatus, ances a, one for each circuit-conductor, are 8 not so much by reason of their strength as of attached to this plate on each side thereof and their tendency to gradually heat and cause opposite each other, the lower one a shown the smoldering of the insulationof the wires as having come into operation. The plate is and instrument-helices and adjacent comconnected to ground G by the wire 10. The

40 bustible material, which not infrequently reprotectors are all alike in construction, and sults in destructive fires. each pair for a pair of conductors constituting The invention consists of a protective apa metallic circuit are united to each other on pliance adapted to be held in supports under the opposite sides of the plate 1 by screws f. spring-pressure, which supports may be line- One incoming conductor 2 connects with the 45 conductor terminal springs and normally end of spring-finger t, and the circuit contin- 5 forming an electrical connection between the ues through the protective device a and the said supports, but adapted to dissever the spring-finger h to conductor 3 and thence to same, opening the circuit, and also to ground the switchboard connections and appliances, the line, if desired; and it consists of a thimfrom whence the circuit returns by way of con- 50 ble provided with a heating-coil at one end ductor 5, springk, protective device a spring j, and conductor 4-. The conductors 2 and 4 are therefore the two ends of the external or main circuit, and the conductors 3 and 5 are the ends of the switchboard continuation thereof.

The springs are provided with holes or slots to receive the ends of the device a and a and the springs 11 and j are prolonged and terminate in narrow ends (3 to hold the carbon-plate air space protectors in position upon the grounding-plate extension 1) p, as fully described in Patent No. 564,084, dated July 14, 1896, granted to A. de Khotinsky.

The springs h, t', j, and are separated and insulated from the grounding-plate l and from each other by the insulating strips or washers b, c, d, and e and are firmly held in place by the screws f.

The protective device constituting the invention is fully shown in the Figs. 2, 8, and a, which are exaggerated in size to more closely show the construction. 12 is a metal thimble which may be stamped or spun into shape and is provided on its end with a stud :0. 16 is a button, of insulating material, fitting snugly in the bottom of the thimble, and 7 is a pin screwed thereinto. The tube 13, of insulating substance, fits tightly into the enlarged end of the thimble. It is slitted longitudinally, as at 18, so that it can be expanded and passed over the metal spool 9, which has an outer flange 19 of the same diameter as that of the tube 13. A fine German-silver wire 11, having an insulating-covering, is wound into a coil 10 upon the spool, and one end thereof is soldered at 17 to the outer flange 19, while the other end is brought out through the slit 18 and soldered to the thimble 12. The solder used in making these two connections is comparatively hard, melting at about 350 Fahrenheit. Instead of German silver the heating-coil may be formed of any suitable metal or alloy.

8 is a tube concentric with the pin 7, having its lower end 20 enlarged to fit the interior of the spool 9, and is provided at its inner extremity with a flange 15, attached by soft solder or similar easily-fusible alloy or metal to the inner flange 1a of the bobbin. The solder used in making this connection may be any soft alloy melting at about 160. The flange or the entire enlarged end of the tube may, if desired, be wholly formed of such easilyfusible metal.

Fig. 3 represents the device assembled and as placed between the spring-fingers,the outer end of the finger 7o embracing the stud 0c and the inner flangej pressing upon the end of the tube 8, the pin 7 passing through the hole in the finger. The circuit extends from the springs t' or j through cylinder 8 and its flange 15 to the flange 14c of the bobbin 9 and from the outer flange 17 thereof through the heating-coil 10 and wire 11 to thimble 12 and the spring 70 or h, as the case may be.

When a dangerous current of the character described traverses the line for a sufficient length of time, the resistance of the heatingcoil causes the development of heat, which is communicated to the spool and acts upon the solder forming the lower portion of the tube or uniting the flanges 14 and 15. This in a short time becomes sufficiently softened and, yielding to the force exerted by the springs j and it, permits them to sever the contact surfaces or flanges 15 and let of the tube 8 and heating-coil spool 9, respectively, bringing the parts into the position illustrated by Fig. 4:. The pin 7 then presses the spring a into contact with the groundingplate 1, and at the same time the circuit is opened between the bobbin 9 and the tube 8, and the line, via springj and pin 7 and plate 1, is grounded.

The device is not liable to become damaged by the melting of the soft solder, and the parts can therefore be resoldered and used indefinitely.

The employment of a protective device which both opens the circuit and grounds its line conductors enables the said device to come into action and shunt the dangerous current to earth without at the same time exercising a similar drain of the central-officebattery current, which otherwise would ensue, leaving other circuits receiving supply from the same battery depleted of their calling-current.

Having thus explained my invention, I claim 1. A protective appliance adapted to be held in supports under spring-pressure and normally forming an electric connection between the said supports but adapted to dissever the same, consisting of a metal thimble provided with a heating-coil at one end, an insulated pin extending from the opposite end through the said coil, and a metal tube concentric with said pin and soldered to the bobbin of the coil, as and for the purpose set forth.

2. A protective appliance adapted to be held in supports under spring-pressure, and normally forming an electric connection between the said supports but adapted to dissever the same; consisting of a metal thimble provided with an insulated heating-coil wound over a metal spool at one end, an insulating-button in the opposite end supporting a metal pin which projects through the axis of said coil, and a metal tube concentric with said pin soldered to the bobbin of the coil, as and for the purpose set forth.

3. A protective appliance composed of two line-conductor terminal springs; a groundplate; and a device between said springs 11ermally forming an electric connection between the same but adapted to dissever said connection and connect one of the springs to ground; the said device comprisin g a thimble 1897, in the presence of two subscribing wit nesses.

ARTHUR S. \VILLIAMS.

Witnesses:

JOSEPH A. GATELY, THOMAS D. LooKWooD. 

